Box Jellyfish: Characteristics, Types & Classification

Instructor: Lauren Posey

Lauren has taught intermediate reading in an English Language Institute, and she has her Master's degree in Linguistics.

In this lesson, you will learn about the classification of box jellyfish, some characteristics shared by this group, and a few of the different species included in it. Find out about the smallest and largest toxic box jellyfish.

A Wide Range

Think about all the jellyfish you have ever heard of. How many species can you name? Did you know that there are over one thousand species of jellyfish, ranging all over the oceans and coastlines? However, there are only 20-30 known species in the box jellyfish group, ranging in size from ten feet long (including tentacles) all the way down to less than an inch.


'Box jellyfish' is actually the common name for the class Cubozoa, which includes a number of different species. Class is a level of taxonomy, or scientific classification, above order, family, genus, and species. That means a class includes more animals than any of the groups below it. As a result, the name 'box jellyfish' can be applied to many different species.


Despite the wide range of species, members of the box jellyfish group do share a number of characteristics. One is the shape of their bell, the top part of the jellyfish where the tentacles attach. Box jellyfish have a square bell, which is where they get their name.

The tentacles of these jellies are attached at the corners of the bell. Some species only have four, while others have a lot, but for all members of the group, the point where tentacles attach to the bell is the same.

Box jellyfish species all have a square bell and tentacles dangling from the four corners
Box Jellyfish

In addition, members of the box jellyfish class have eyes, which other types of jellyfish do not have. They can see images as well as light and dark, which helps them find prey and avoid predators.

Box jellies can also swim actively. Most jellyfish can only keep themselves near the current, and for the most part, simply drift with the current. However, box jellyfish can actively propel themselves around, moving as fast as 90 meters per minute! This means they can actively hunt prey and avoid predators, which other jellies cannot do.

Finally, there are many members of this group that are extremely toxic. All jellyfish have nematocysts, or stinging cells, but the toxin found in some species of box jellyfish is the most potent of any jellyfish.


Since 'box jellyfish' is a common name applied to a number of different jellies, the number of species included in the category varies. There are anywhere from 20-30 species of box jellyfish, occurring along a variety of coastlines in warm areas around the world.

Fatally Toxic Box Jellyfish

There are several species of box jellyfish known to be fatal to humans, and most of them live off the coast of Australia. One is the smallest box jelly, the Irukandji jellyfish (Carukia barnesi). It is less than an inch long, but its sting causes a severe reaction in humans, sometimes leading to heart failure and death.

The largest box jellyfish is also quite deadly. The Australian sea wasp (Chironex fleckeri) can cause heart failure and death in an adult human within minutes of stinging them. These box jellies can grow to be the size of a basketball, with tentacles up to ten feet long. It is difficult to say which species might be deadlier, especially considering their size difference, but avoiding either one seems like a good idea!

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